The objectives of this study are to compare the safety and efficacy of Antocin maintenance therapy to placebo maintenance therapy among women with preterm labor who have achieved uterine quiescence with Antocin i.v. therapy. This is a multicenter study consisting of an open-label Antocin intravenous treatment phase followed by a randomized, parallel group, double-blind, placebo-controlled, subcutaneous maintenance treatment phase. Only those subjects who achieve uterine quiescence during the initial Antocin i.v. treatment will be randomized to receive maintenance therapy. Subsequent intravenous treatments with Antocin i.v. will be given to qualified subjects. A two year infant safety follow-up is also required. Eleven women and their children were enrolled into the study. Eight children will have their 2 year follow-up visits within the next year and data analysis will be done.